Light collector for optical organ

ABSTRACT

In an electro-optical organ which includes a device, such as, a rotating disc with numerous concentric tracks of varying opacity representing respective musical tones or sounds and a light source diverting light through all of the tracks, for establishing time-varying light beams representing the musical tones which pass through a relatively long and narrow slit, and a photocell for generating electrical signals in audible to such light beams which signals are employed, for example, in an amplifier and loudspeaker arrangement, for producing corresponding auidble sounds; a light collector is provided for transmitting the light beams from the slit to the photocell and is constituted by a body of light transmitting material having pickup and output ends disposed at the slit and photocell, respectively, and including a first substantially planar portion which tapers from a relatively large width corresponding to the length of the slit at the pickup end to a relatively smaller width at the output end, and second portions directed from the first planar portion at substantial angles to the latter and extending along the first planar to the output end from locations spaced from the output end, with the widths of such second portions increasing progressively therealong toward the output and so as to substantially equalize the cross-sectional areas of the light-transmitting body between its pickup and output ends. The aforementioned second portions may be constituted by longitudinal corrugations in the planar portion of the lighttransmitting body or may extend along the opposite side edges of such planar portion.

United States Patent 1 Bartok et al.

[ LIGHT COLLECTOR FOR OPTICAL ORGAN [75] Inventors:- Stephen Bartok,Gardena; George J.

Klose, Redondo Beach; George W. Stewart, Costa Mesa, all of Calif. [73]Assignee: Opsonar Organ Corporation, Bronx,

[22] Filed: Sept. 29, 1972 [21] Appl. No.: 293,738

[52] US. Cl. 84/1.l8, 250/227, 350/96 R [51} Int. Cl. Gl0h 3/06 [58]Fieldof Search 84/l.l8; 250/227; 350/96 R [5 6] References Cited 1UNITED STATES PATENTS 3,177,470 4/1965 Galopin 84/l.l8 X 3,411,01111/1968 Genahr et a1... 250/227 3,752,561 8/1973 Klemt 350/96 R2,318,144 5/1943 Darke 84/1.l8 2,855,539 10/1958 Hoover .....350/96 R X2,945,958 7/1960 Morris 84/1.18 X 3,263,070 7/1966 Hine..... 350/96 R X3,307,020 2/l967 Cahill... 350/96 R X 3,405,222 10/1968 ,Heinzl 84/l.l83,484,530 12/1969 Rupert 84/l.l8 3,599,001 8/1971 Rolnik et a1. 250/227X 3,652,776 3/1972 Milde 84/l.l8 X 3,692,383 9/1972 Herod et al. 350/96R 3,694,902 10/1972 Apgar et a1. 350/96 R X Primary Examiner-Richard B.Wilkinson Assistant Examiner-Stanley J. Witkowski Attorney, Agent, orFirmAlvin Sinderbrand 51 Mar. 26, 1974 [57] ABSTRACT In anelectro-optical organ which includes a device, such as, a rotating discwith numerous concentric tracks of varying opacity representingrespective musical tones or sounds and a light source diverting lightthrough all of the tracks, for establishing time-varying light beamsrepresenting the musical tones which pass through a relatively long andnarrow slit, and a photocell for generating electrical signals inaudible to such light beams which signals are employed, for example, inan amplifier and loudspeaker arrangement, for producing correspondingauidble sounds; a light collector is provided for transmitting the lightbeams from the slit to the photocell-and is constituted by a body oflight transmitting material having pickup and output ends disposed atthe slit and photocell, respectively, and including a firstsubstantially planar portion which tapers from a relatively large widthcorresponding to the length of the slit at the pickup end to arelatively smaller width at the output end, and second portions directedfrom the first planar portion at substantial angles to the latter andextending along the first planar to the output end from locations spacedfrom the output end, with the widths of such second portions increasingprogressively therealong toward the output and so as to substantiallyequalize the cross-sectional areas of the light-transmitting bodybetween its pickup and output ends. The aforementioned second portionsmay be constituted by longitudinal corrugations in the planar portion ofthe light-transmitting body or may extend along the opposite side edgesof such planar portion.

7 Claims, 14 Drawing Figures LIGHT COLLECTOR FOR OPTICAL ORGANBACKGROUND OF THE INVENTION This invention relates to light collectorsand especially to light collectors used in optical organs.

One type of optical organ utilizes a rotating disc with numerousconcentric tracks; and a lamp that shines light through all of thetracks. A photocell on the side of the tracks opposite the lamp picks uplight from any of the tracks and converts the light to electricalsignals that are amplified and played through a loudspeaker. A slit isplaced between the tracks and photocell to permit light from only anarrow region of each track to reach the photocell. The region near theslit where light from the numerous tracks can be picked up is normallynarrow and long. For example, in one organ wherein 7 record tracks areprovided which are radially spaced apart by 0.055 inches, the pickupregion can be covered by a rectangle which is approximately 3 incheslong and less than one-tenth inch thick. All of the light could bepicked up by a photocell which was at least 3 inches long. However,photocells of this size are expensive. One type of photocell which canbe used is con- .structed from a crystal of silicon. In order to obtainphotocells of 3 inches length, crystals would have to be grown whichwere at least 3 inches in diameter, or at least 6 inches in diameter toutilize most of the crystal material, and such crystals are difficultand expensive to grow. Furthermore, even if such long photocells wereavailable, special care would have to be taken to assure there was nodead spot" along the length of the photocell which did not produce asmuch current for a given light intensity as was produced by the otherregions of the cell. Any such dead spot could result in one of thetracks being played with much less intensity than the other tracks.

OBJECTS AND SUMMARY OF THE INVENTION An object of the present inventionis to provide an optical organ which can utilize one or a limited numberof relatively small photocells, and wherein the photocells canaccurately reproduce recorded sounds even if there are some smalllocalized dead spots in the photocells.

Another object of the invention is to provide a simple and efficientlight collector for concentrating light received from a long thin areaonto a shorter but thicker area.

In accordance with one embodiment of the present invention, an opticalorgan is provided which utilizes a photocell of small dimensions toreceive time-varying light patterns that are originally arranged along apickup region that is much wider than any dimension of thephotocell. Theorgan utilizes a light collector with a pickup end that substantiallycovers the pickup region where light patterns are received from anoptical record, and an output end where the light is delivered to thephotocell. The light collector also has an intermediate portioncontaining surfaces for internally refleeting light along predeterminedpaths, from each area of the pickup region where light from one opticaltrack is received to the output end. The intermediate portion is formedso that at least some to the light paths include a predetermined limitednumber of internal reflections.

In one type of light collector, the light collector has a main sheet orplanar portion extending from the pickup end to the output end and istapered in width along at least some of its length so that it isprogressively narrower nearer the output end. At least two auxiliarysheets or portions intersect the main sheet, and each auxiliary sheet isprogressively wider at locations nearer the output end. The auxiliarysheets or portions may be constituted by corrugations extendinglongitudinally in the main sheet or planar portion, or may extend alongthe opposite side edges of the main sheet.

In another light collector, a main sheet is provided which is tapered inwidth so that its edges reflect light to a central portion of the sheet.The central portion has a recess with numerous inclined walls thatreflect light out of the plane of the sheet.

The novel features that are considered characteristic of this inventionare set forth with particularity in the appended claims. The inventionwill best be understood from the following description when read inconnection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial, simplifiedperspective view of an optical organ including a light collector of theinvention; I

FIG. 1A is a sectional view taken on the line 1A1A of FIG. I;

FIG. 2 is a partial, perspective view of an organ with a light collectorconstructed in accordance with a second embodiment of the invention;

FIG. 3 is a perspective view of a light collector constructed inaccordance with a third embodiment of the invention;

FIG. 4 is a side elevation view of of FIG. 3;

FIG. 5 is a view taken on line 55 of FIG. 4;

FIG. 5A is a view taken on the line 5A-5A of FIG.

the light collector FIG. 6 is a view taken on the line 66 of FIG. 4;

FIG. 7 is an enlarged side elevation view of the region 7-7 of FIG. 4;

FIG. 8 is a perspective view of a light collector constructed inaccordance with a fourth embodiment of the invention, the lightcollector being similar to that of FIG. 3 except that it includesnumerous slits at its pickup end that form light collecting fingers;

FIG. 9 is a perspective view of a light collector constructed inaccordance with a fifth embodiment of the invention;

FIG. 10 is a side elevation view of the light collector of FIG. 9;

FIG. 11 is a partial rear elevation view taken on the line l1ll of FIG.10; and

FIG. 12 is a sectional view taken on the line 12-12 of FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS opposite the lamp. The maskblocks the passage of light except at a narrow, long slit formed in themask. Light from the record that passes through the slit 20 can be madeto reach a photocell 22 that converts the light to electrical signals.The electrical signals pass through an amplifier 23 and drive aloudspeaker 25.

Light from the region of the slit 20 is carried to the photocell 22 by alight collector 24. The light collector 24 has a pickup end 26 which cansubstantially cover and therefore pick up light form the slit 20, and anoutput end 28 where the light which is picked up is delivered to thephotocell. The organ must be constructed so that light from any of thetracks 12 that passes through the mask 20 does not reach the photocelluntil a selected key 30 of a keyboard 32 is depressed by a musician. Toprovide for this, the pickup end portion 26 of the light collector isprovided with numerous long slits that form individual light collectingfingers 34. The light collector 24 is formed of a transparent resilientmaterial, such as an acrylic plastic and the light fingers 34 normallyassume a position wherein their tips lie a distance to the side of theslit 20. When any one of the light fingers, such as the light finger34a, is deflected over the slit 20, the light finger picks up light fromone of the tracks 12 and permits light from that track to pass to thephotocell 22. Each key 30 is connected by a pivotally mounted crank 36and a long rod 38 to a corresponding light finger 34, so that when a key30 is depressed, the rod 38 slides and deflects a corresponding lightfinger over the slit. g

The pickup region, which is the area immediately over the slit 20 wherelight can be picked up, is wide and thin. The initial portion 40 of thelight collector that lies immediately past the inner ends of the fingers34 is also wide and thin. However, the light collector also has anintermediate portion 42 which collects light from the wide thin portion40 and directs it onto the output end 28 of the light collector. Theoutput end 28 has a width W, which is much less than the width W Of theinitial portion 40. This permits a photocell 22 to be used which hasonly a small width W It would be possible to utilize a light collectorwithout the middle portion 42 and output end 28, so that the lightcollector would end at the initial portion 40 which is wide and thin.However, the photocell for picking up light would then have to have awidth W equal to that at the pickup end 26 of the light collector. Thiscan lead to considerable expense, inasmuch as photocells suitable for anorgan and which have a length of substantially more than one inch areexpensive. One series of records 10 has 57 record tracks spaced 0.055inches from one another, so that a pickup region of 3 inches in width isrequired to pick up light from all tracks. In some organs, twophotocells are utilized, one picking up a group of twenty tracksrepresenting chords or other accompaniment patterns of notes, and theother picking up 37 tracks representing sustained notes. However, the 37track group has a length of about 2 inches, and a photocell of even 2inches in length is expensive. Such a photocell is not required becausethe light collector 24 can concentrate light to a more compact area thatcan be covered by an inexpensive photocell. Photocells of a standardsize such as 1 cm. by 2cm. are available at low cost, and the output end28 of the light collector can be formed so it can be covered by aphotocell of this size.

An important advantage of the light collector 24 is that it distributesthe light from any light finger 34 over a large area of the output end28. The tip of each finger 34 can cover a small pickup area where it canreceive light from one optical track. If all of this light were incidenton a small area of a photocell, then it would be necessary that allregions of the photocell be equally sensitive to light. If the photocellhad a dead area" that had a low sensitivity, and if all of the lightfrom a light finger were incident only on that dead area, then only avery low level of sound could be obtained from the corresponding opticaltrack. The light collector 24, however, distributes the light picked upat a small pickup area, so that although some of the light from anypickup area may fall on a dead area of a photocell, most of the lightfrom any pickup area will be distributed over other photocell areaswhich are more sensitive. Accordingly, any diminution of output due tothe dead area of the photocell will be very small and generallyunnoticable.

The intermediate portion 42 of the light collector is tapered in widthW, as measured between its opposite sides, so that the light collectoris of progressively smaller width at.locations progressively closer tothe output end 28. In addition, the middle portion 42 of the lightcollector has folds or corrugations formed therein along its length, sothat the corrugations appear in a cross section taken along the width ofthe light collector as in FIG. IA. The corrugations progressivelyincrease in height H at locations progressively closer to the output end28 of the light collector. Accordingly, although the width of the lightcollector progressively decreases, the cross-sectional area of the lightcollector does not change much, if at all, between the pickup end 26 orinitial portion 40 and the output end 28.

The exact dimensions of each portion of the light collector 24 must bechosen so that approximately the same proportion of light reaching eachpickup area, or each light finger 34, reaches the output end 28. Thedesign of a light collector can be a difficult problem. In the lightcollector of FIGS. I and 1A, most of the light or light beams reachingthe initial area 40 undergo one or more reflections prior to reachingthe output end 28. The light collector 24 is designed -so that the lightbeams from any region of the initial portion 40 travel alongpredetermined paths. At least some of these paths include apredetermined limited number of internal reflections prior to the lightbeams reaching the output end 28. This construction may be contrastedwith the use of a cylindrical rod or other simple piece of transparentmaterial wherein light hitting the sides of the rod can be picked up ateither end of the rod by reason of diffusion of light due toirregularities in the surface of the rod which result in diffusion ofthe light in all directions. In the case of such a rod, the number ofinternal reflections of light is not limited and the proportion of lightreaching either end from any pickup area of the pickup region is unknownand generally grossly unequalto the proportion from some other pickupareas. The analysis of a light collector can be extremely complex wherethe internally reflecting surfaces are compoundly curved, that is, wherelocations on the surface are simultaneously curved about more than oneaxis. In order to permit rigorous analysis of a light collector, toassure that approximately the same proportion of light incident on anyof the numerous pickup areas reaches the output end, the light collectorshould contain primarily planar surfaces.

FIG. 2 illustrates an organ constructed in accordance with anotherembodiment of the invention which utilizes a light collector 50containing substantially only planar surfaces. The light collectortherefore can be rigorously analyzed and designed to assure thatapproximately the same high proportion of light beams from all pickupareas reach the photocell. The organ of FIG. 2 utilizes a row ofpivotally mounted light shutters 52 which have light blocking portions54 that normally block the passage of light that emanates from therecord and passes through the slit 20. However, when one of the rods 38ais pushed, it pivots one of the shutters 52a so that light can reach apickup area at the pickup region 56 of the light collector. Lightreceived at the pickup region 56 passes along a middle region 58 to anoutput end 60 of the light collector. A photocell indicated at 62 ispositioned directly over (and normally against) the output end 60 topick up the light.

The middle region 58 of-the light collector 50 includes a sheet orplanar portion 64 which is tapered in width so it is of progressivelynarrower width at locations progressively closer to the output end 60.The sheet 64 is also corrugated, having four corrugations 66, 67, 68 and69 which are of progressively greater height at locations progressivelycloser to the output end. Thus, although the overall width of the lightcollector decreases towards the output end, the crosssectional area ofthe light collector undergoes a smaller rate of decrease in area, ifany, as locations pr0gres vsively closer to the output end. The middleportion 58 of the light collector can also be described as including amain sheet 64 with slots 70, 71, 72 and 73 therein, and as includingauxiliary sheet portions formed by each side of the corrugations 66-69which intersect the main sheet 64 at the edges of themain sheet, andwith the planes'of the auxiliary sheet portions extending perpendicularor at substantial angles to the plane of the main sheet 64. Each of theauxiliary sheets is tapered in width so that itis progressively wider atlocations progressively nearer the output end 60 of the light collector.In addition, the pairs of auxiliary sheets formed by the corrugations66-69 are thicker than the main sheet 64.

FIGS. 3-7 illustrate a light collector 80 constructed in accordance withstill another embodiment of the invention, this light collector beingrelatively small and economical to mold and yet being highly efficient.The light collector 80 includes a pickup end 82 which can lie over aregion where light is received, an output end 84 which can carry a smallphotocell, and a middle portion 86 which collects light so thatapproximately the same proportion of light from individual small pickupareas at the pickup end 82 reach the output end 84. The light collectorincludes a main sheet portion 87 which extends between the pickup andoutput ends, which is of uniform width along a portion near the pickupend 82, and which is tapered in width along the middle portion 86 of thelight collector. The light collector also includes a pair of auxiliarysheets 88, 90, which intersect the opposite edges of the main sheet 80along the tapered portion of th'einain sheetfand provide the lightcollector with a corrugated cross-section. The auxiliary sheets 88, 90are tapered in width, increasing in width from a substantially zerowidth at one end 92 where the main sheet begins to taper to a maxi mumwidth at the output end 84 where the main sheet is of minimum width. Asillustrated in FIG. 5A, each auxiliary sheet such as sheet 90 intersectsthe main sheet 87 primarily perpendicular to the plane of the mainsheet, that is, at more than 45, the actual angle B being about Thelight collector also has a sheetlike portion at the output end 84, whichfunctions only to brace the auxiliary sheets. Three bracket portions 94,96, and 98 project from selected parts of the main sheet to providemounting brackets for supporting the light collector on an organ frame.

The light collector is constructed in accordance with a rigorousanalysis of light beams receivable at any pickup area of the pickup end82, and receivable within predetermined solid angles, to assure thatapproximately the same proportion of light from any of the pickup areasreaches a photocell at the output end 84. Among the details ofconstruction, it may be noted that the edges 100, 102, where theauxiliary sheets 88, intersect the main sheet 80, are beveled on theoutside, so the outer corner surface is angled from the faces of boththe main sheet 80 and the adjacent auxiliary sheet 88 or 90. Thebeveling is provided to assure that light beams passing within the mainsheet and striking an edge of the main sheet will be internallyreflected into the auxiliary sheet. The paths of two light rays 101 and103 are illustrated, the path of ray 101 including reflections at thebeveled edge 102 and at the opposite edge of auxiliary sheet 90, and thepath of ray 103 including a reflection at the beveled edge 102. Thelight collector is constructed of a material, such as an acrylic plasticwhich has an index of refraction of approximately 1.5. Accordingly, atotal internal reflection will occur at an angle of incidence of morethan about 42. It has been found that the auxiliary sheets 88, 90generally must be thicker than the main sheet 87 from which they receivelight in order to insure capture of a high proportion of light from themain sheet.

The light collectors are most economically produced by molding,especially by injection molding, and the speed of production can beincreased by utilizing thin sheet surfaces. The thickest portions of thelight collector are generally at the auxiliary sheets 88, 90 whichgenerally must be thicker than the main sheet 87. The

thickness of the auxiliary sheets is minimized by making the main sheet87 especially thin. While a thin main sheet 87 can efficiently transmitlight, it sometimes may not be efficient in picking up light at itspickup end. The ability of the light collector to pick up light isincreased by enlarging the pickup end portion 82 so that it can pick uplight over a thicker area or wider angle. The use of an increasedthickness at the pickup end 82 of the main sheet, in a main sheet 87that is thin along most of its area, plus the thicker auxiliary sheets,results in efficient light pickup and collection in a light collectorthat can be injection molded at a rapid rate, and which therefore can beproduced economically. It may be noted that the light collector has acentral bulging portion or rib 104 extending along the length of themiddle portion 86. The rib 104 is provided to dissipate a higherproportion of light received near the center of the pickup region 82, tomore nearly equalize the proportion of light from all of the pickupareas that reach the output end 84.

FIG. 7 illustrates details of the thickened tip or pickup end portion 82of the light collector. The light collector is of uniform shape allalong the width of the pickup end 82. The thick pickup end has a pair offacets 106, 108 that make the tip convex instead of merely flat. Theconvex end helps to direct light received over a considerable angle Afrom the slit 20 in the mask 18, so that light within the angle willpass along the light collector and reach the output end. By enabling thepickup of light over a considerable angle A, such as 30, a largerproportion of available light is picked up, so that a larger andtherefore less noisy signal is obtained from the photocell.

FIG. 8 illustrates a light collector constructed in accordance withanother embodiment of the invention, wherein the light collector 120 issubstantially identical to the light collector 80 of FIG. 3, except thatits pickup end portion 82 has numerous slits which divide the end intolight collecting fingers 122. The light collecting fingers 122 operatein the manner indicated for the fingers 34 of the light collector ofFIG. 1, each of the fingers being normally lying in a position whereinthey cannot pick up light from an optical track.

FIGS. 9-12 illustrate a light collector 130 constructed in accordancewith yet another embodiment of the invention. The light collector 130includes a sheet portion or sheet 132 which has a pickup end 134 andwhich is tapered between the pickup end 134 and another, opposite end136, to form a substantially parabolic edge. However, the output region138 where a photocell 140 can be located, is not at the second end 136where the sheet is of minimum width. Instead, the output region islocated at a middle or deflector portion 142 of the sheet. The deflectorportion 142 is thickened and has a recess 144. The recess 144 hasinclined walls such as walls 146, 148 best illustrated in FIG. 12, whichreflect light out of the plane of the sheet 132.

The tapered portion of the sheet 132 has an edge 150 of substantiallyparabolic shape, as viewed in a front elevation view, for internallyreflecting light beams that enter the pickup end 34 so they are receivedat the deflector portion 142. The beveled walls 146 of the recess 1 frompickup areas near the middle of the pickup end 134. In addition, a pairof mounting bosses 154 are provided which facilitate mounting of thelight collector.

Thus, the invention provides an optical organ which can utilize alimited number of relatively inexpensive photocells, even though thelight patterns to be picked up extend along a wide pickup region. Theorgan utilizes a light collector which concentrates the light from awide thin region to a less wide but thicker region that can be coveredby a relatively inexpensive photocell. The light collector carriesapproximately the same proportion of light from each pickup area, wherelight from each optical track is received, to the photocell. The lightcollector has a pickup end where it receives light, an output end whereit' delivers light to a photocell, and an intermediate portion whichcarries light along predetermined paths from each pickup area to theoutput end, at least some of the paths includinga limited number ofinternal reflections. In some light collectors, some of the rays arereflected at only one or two edge regions of the sheet-like portions.The light collector can be constructed with a main sheet of transparentmaterial with a portion that is tapered in width so it is progressivelynarrower in width at locations progressively further from the input end.In one type of collector, a plurality of auxiliary sheets are providedwhich are of progressively greater width at locations progressivelyfurther from the input end of the light collector. In another type oflight collector, the main sheet has a central portion with a recess thathas inclined walls for reflecting light largely perpendicular to thesheet. While the light collector is preferably uncoated to minimizecosts, it is possible to apply aluminum or other reflective coatings toselected surfaces.

Although particular embodiments of the invention have been described andillustrated herein, it is recognized that modifications and variationsmay readily occur to those skilled in the art and consequently it isintended that the claims be interpreted to cover such modifications andequivalents.

What is claimed is:

1. An optical organ comprising:

a light collector constituted by a body of lighttransmitting materialhaving spaced apart pickup and output ends and including a firstsubstantially planar portion which tapers in width from a relativelylarge width at said pickup end to a relatively smaller width at saidoutput end, and second portions directed at substantial angles from saidfirst planar portion and extending along the latter to said output endfrom locations spaced from said output end, the widths of said secondportions increasing progressively therealong in the directions towardsaid output and so as to substantially equalize the cross-sectionalareas of said body at said pickup and output ends;

means for establishing time-varying light beams representing sounds andwhich are selectively directed into said first planar portion of thelighttransmitting body at respective spaced locations across said pickupend;

photosensitive means positioned at said output end of thelight-transmitting body for generating electrical signals in response tolight beams transmitted through said body; and

means responsive to said electrical signals for generating correspondingsounds.

2. An optical organ according to claim 1; in which said second portionsof the light-transmitting body have greater thicknesses than said firstplanar portion.

3. An optical organ according to claim 1; in which said first planarportion has corrugations extending longitudinally therein with theflanks of said corrugations increasing in depth to said output end fordefining said second portions.

4. An optical organ according to claim 1; in which said first planarportion has opposite side edges which converge in the directiontowardsaid output end, and said second portions extend along said side edgesof said first planar portion.

5. An optical organ according to claim 4; in which said side edges alongwhich the second portions extend are bevelled.

6. An optical organ according to claim 1; in which the edge of saidfirst planar portion at said pickup end of the light-transmitting bodyis relatively thicker than the remainder of said first planar portionand is convex.

7. An optical organ according to claim 1; in which said first planarportion has light-dissipating means centrally located therein forminimizing the proportion of the light reaching said output end from thecentral part of said pickup end.

1. An optical organ comprising: a light collector constituted by a bodyof light-transmitting material having spaced apart pickup and outputends and including a first substantially planar portion which tapers inwidth from a relatively large width at said pickup end to a relativelysmaller width at said output end, and second portions directed atsubstantial angles from said first planar portion and extending alongthe latter to said output end from locations spaced from said outputend, the widths of said second portions increasing progressivelytherealong in the directions toward said output and so as tosubstantially equalize the cross-sectional areas of said body at saidpickup and output ends; means for establishing time-varying light beamsrepresenting sounds and which are selectively directed into said firstplanar portion of the light-transmitting body at respective spacedlocations across said pickup end; photosensitive means positioned atsaid output end of the lighttransmitting body for generating electricalsignals in response to light beams transmitted through said body; andmeans responsive to said electrical signals for generating correspondingsounds.
 2. An optical organ according to claim 1; in which said secondportions of the light-transmitting body have greater thicknesses thansaid first planar portion.
 3. An optical organ according to claim 1; inwhich said first planar portion has corrugations extendinglongitudinally therein with the flanks of said corrugations increasingin depth to said output end for defining said second portions.
 4. Anoptical organ according to claim 1; in which said first planar portionhas opposite side edges which converge in the direction toward saidoutput end, and said second portions extend along said side edges ofsaid first planar portion.
 5. An optical organ according to claim 4; inwhich said side edges along which the second portions extend arebevelled.
 6. An optical organ according to claim 1; in which the edge ofsaid first planar portion at said pickup end of the light-transmittingbody is relatively thicker than the remainder of said first planarportion and is convex.
 7. An optical organ according to claim 1; inwhich said first planar portion has light-dissipating means centrallylocated therein for minimizing the proportion of the light reaching saidoutput end from the central part of said pickup end.